Two weeks ago President-elect Donald Trump chose USMC General (ret.) James ‘Mad Dog’ Mattis as his secretary of defense. Unlike Israel the United States has a tradition of appointing a civilian as secretary of defense, to insure civilian oversight of the military. If Mattis is approved by the Senate he will be the first general to hold the position since George Marshall in the ‘50s.The desire to appoint a civilian stems from the fact that the main role of the secretary of defense isn’t to command troops in the field – the Unified Combatant Command as well as the national security adviser and the president are responsible for that. The primary function of the secretary of defense is to shape the military strategy and the defense force buildup of the United States. Therefore his business is the civil context of the military, including the size of the military budget, and the interface with the defense industries and the House of Representatives.These are issues that the American public must engage with, and not the military and its senior commanders.When a person has served as a soldier for over 30 years, we can assume that, as the saying goes, he will sit where he stands. His mindset, the focus of his work and his expertise will be on military action. In Israel, for example, some of the former senior military officers who served as defense minister wrongly thought the defense minister was a representative of the military in the government and not the government supervisor of the military. Nevertheless, the appointment of General Mattis is extraordinary.In the book The March Up (Bantam, 2003) written by Francis “Bing” West and Maj. Gen. (ret.) Ray Smith, USMC, they describe the famed 1st Marine Division’s march on Baghdad.During Operation Iraqi Freedom they acquired an SUV and joined the unit that was spearheading the assault. They described the division commander, Gen. James Mattis, as a “Marine’s Marine,” and wrote that “Mattis’s life, not merely his career, had centered on command in the field. He had a remarkable record of infantry leadership: a rifle platoon; a rifle company; an infantry battalion like Conlin’s; an infantry regiment; and a Navy-Marine Task Force” (page 18). In 2001, as the commander of that task force, “Mattis had taken a reinforced battalion 800 kilometers from ships in the Indian Ocean to a dirt airstrip in Afghanistan – no small feat” (page 78).Despite the fact that the authors served in Vietnam as Marine infantry officers and were experienced in all aspects of combat “from the ground up,” they were impressed by Mattis, who commanded his division in a swift and aggressive manner that reminded many of the way general Patton led his troops in WWII (Marines will probably prefer to compare him to USMC Gen. “Chesty” Puller).Mattis’s 1st Marine Division had feinted and slashed through six Iraqi divisions and, ignoring orders to slow down, had seized the eastern half of Baghdad weeks ahead of schedule.MATTIS LED Marines into combat against a changing enemy, from insurgents to regular army formations in the Gulf War, Afghanistan and Iraq, and was awarded a bronze star for valor. Though Mattis appears to be what is known in the IDF as a plain, outspoken “Golanchick” (member of the Golani Brigade), he is actually an avid student of warfare who understands geopolitical strategy as well as the new trends in the battlefield. As the commander of US Central Command he was also an important diplomatic representative of the US administration in the Middle East.He opposed the nuclear agreement with Iran, which he saw as a major threat to regional stability, and criticized the Israeli settlement enterprise as an obstacle to peace.The Chairman of the Joint Chiefs of Staff, USMC Gen. Joseph Dunford, as well as USMC Gen. John F. Kelly, selected by President-elect Trump for the position of Secretary of Homeland Security, served under Mattis during the campaign in Iraq. West and Smith wrote that Dunford “was the commander most apt to pick up on Mattis’s invitation to offer alternatives to the division’s planned scheme of maneuver. His regiment, with more than a thousand vehicles and six thousand men, had been the division’s Main Effort since crossing the Euphrates” (page 135). That campaign, as well as the fighting in Fallujah, formed a close comradeship between the three officers. As such Mattis will probably refrain from becoming Dunford’s boot-camp drill instructor and work closely with him.As someone who understands the limits of power, the importance of the US’s relationships with its allies, the need for proper planning and preparations and the importance of a responsible and restrained strategy, both domestically and internationally, Mattis can restrain the president-elect and prevent him from dismantling the American system in the name of anti-establishment. Mattis very well may be the responsible adult in the room.Before embarking for the campaign in Iraq Mattis posted a letter to 1st Marine Division which ends with the phrase: “Demonstrate to the world there is ‘No Better Friend, No Worse Enemy’ than a US Marine.” As a senior member of President-elect Trump’s cabinet, Mattis will probably try to implement exactly that policy.The author is the coordinator of the Military & Strategic Affairs program at the Institute for National Security Studies (INSS).